Resin composition laminate and laminate film

ABSTRACT

A resin composition comprising: a polyvinyl alcohol; and an inorganic laminar compound having an aspect ratio of not less than 50 and not more than 5000, which has a volume ratio of (inorganic laminar compound/polyvinyl alcohol) in the range of (5/95) to (30/70); and a laminate or laminate film comprising, as at least a portion thereof, a layer or portion (1) comprising such a resin composition. The resin composition, laminate or laminate film may exhibit a good gas barrier property while substantially retaining a good film strength.

Application Ser. No. 08/525,620, filed Sep. 22, 1995 was, in turn, theNational Phase of International Application PCT/JP95/00072 filed Jan.24, 1995 which designated the U.S. and that International Applicationwas not published under PCT Article 21(2) in English.

TECHNICAL FILED

The present invention relates to a resin composition having an excellentgas barrier property, a laminate or laminate film which comprises atleast one layer (or at least a portion) comprising such a resincomposition, and a shaped (or molded) article comprising a portion ofthe resin composition.

BACKGROUND ART

A film having a gas barrier property (gas barrier film) as a kind offunctional film has widely been put to practical use in the fields offood, medicine, agricultural chemicals, cosmetics, etc., whereincontents to be contained therein are stored or protected while the“quality” of the contents is liable to cause a problem. One of suchimportant uses of the film includes a field of “packaging”.

Packaging, i.e., making or putting an object into a package or wrap, orthe material for the packaging is desired to have a wide variety offunctions. For example, such functions of packaging may include:mechanical protective property, safety, sanitary property, workability,adaptability to goods (transparency, printability, heat sealingproperty), utility, profitability, etc. Among these functions, a “gasbarrier property” to various gases, as one of the factors in theabove-mentioned storability or protective property, is an importantproperty for affecting the storability of the above contents such asfood. Along with recent diversification in the form of goodsdistribution or in packaging technique, intensification of additivecontrol, change in taste, etc., the importance of the gas barrierproperty has to been increased more and more. On the other hand, the gasbarrier property has heretofore been a serious weak point of ordinaryplastic materials.

Factors which can deteriorate a food include oxygen, light, heat and/ormoisture. Among these factors, oxygen has been considered to be asubstance causing such deterioration. A material having a gas barrierproperty (gas barrier material) is a material which has a main functionof effectively intercepting oxygen. Such a gas barrier material exhibitsthe function of intercepting oxygen, and simultaneously exhibits afunction which is essential for various measures for controlling thedeterioration of food (such as gas charging and vacuum packaging). Thegas barrier material has been utilized very effectively in many fieldssuch as food packaging inclusive of confectionery bags, bags for driedbonito, pouches for retorted foods, containers for carbonated drinks,etc., or packaging for cosmetics, agricultural chemicals, and medicaluse, on the basis of its barrier function to various kinds of gases suchas oxygen, organic solvent vapors, aromas; or on the basis of itsfunction of preventing corrosion, odor, sublimation, etc., based on thebarrier function thereof.

Among films comprising a thermoplastic resin, those films comprisingoriented polypropylene, polyester, polyamide, etc., particularly haveexcellent mechanical property, heat resistance, transparency, etc., andtherefore these films are widely used as a packaging material. However,in a case where a film comprising such a material is used for foodpackaging, since the barrier property thereof to a gas such as oxygen isinsufficient, the food as the contents in the package is liable to bedeteriorated due to degradation based on oxidation, or the function ofaerobic bacteria, etc. Furthermore, in such a case, an aroma componentof the food permeates the package to be diffused to the outside of thepackage. As a result, there tend to occur various problems such that theflavor of the food is lost, or the contents are wetted with outsidemoisture due to the penetration of such moisture and the taste thereofbecomes worse. Accordingly, when a film of the above-mentioned materialsuch as polypropylene is used for food packaging, it is usual to adopt amethod wherein another film (or layer) having an excellent gas barrierproperty is laminated onto the film of the above-mentioned material.

As a transparent plastic raw material having a small gas permeability(i.e., a large gas barrier property), there have heretofore been knownsome films comprising a raw material such as polyvinyl alcohol,polyethylene-vinyl alcohol copolymer, and polyvinylidene chloride-typeresin. However, these plastic materials have an oxygen permeability to acertain degree which is never negligible, while a metal or glass rawmaterial to be used for canned foods or bottled foods only has asubstantially no oxygen permeability.

As a method of imparting a gas barrier property or increasing the gasbarrier property of a resin, there has been known some methods. Forexample, Japanese Laid-Open Patent Application (KOKAI) No. 30944/1991(i.e., Hei 3-30944) describes a process for producing a coated filmwherein a coating composition comprising polyvinyl alcohol and synthetichectorite in a wt. ratio of 20:80 is applied onto a biaxially orientedpolyethylene terephthalate (OPET), and then dried.

However, such films provided by the above-mentioned conventionaltechniques still do not have a sufficient gas barrier property, and isnot a satisfactory film having a gas barrier property suitable forpractical use.

An object of the present invention is to provide a resin composition, alaminate, or a laminate film which has solved the above-mentionedproblems.

A more specific object of the present invention is to provide a resincomposition, a laminate, or a laminate film having a gas barrierproperty at a good level.

DISCLOSURE OF INVENTION

As a result of earnest study, the present inventors have found that aresin composition having an excellent gas barrier property has beenprovided by constituting a resin composition while an inorganic laminarcompound having a specific aspect ratio is combined with a polyvinylalcohol as a specific resin in a specific volume ratio. As a result offurther study, the present inventors have also found that the excellentgas barrier property of such a resin composition is substantiallyretained, even when a laminate or laminate film is constituted while atleast a layer (or portion) comprising the above-mentioned resincomposition is disposed on a base material, etc.

The laminate according to the present invention is based on the abovediscovery and comprises: a polyvinyl alcohol; and an inorganic laminarcompound having an aspect ratio of not less than 50 and not more than5000, which has a volume ratio of (inorganic laminar compound/polyvinylalcohol) in the range of (5/95) to (30/70).

The present invention also provides a laminate comprising: a basematerial, and at least one layer disposed thereon comprising a resincomposition; which comprises a polyvinyl alcohol, and an inorganiclaminar compound having an aspect ratio of not less than 50 and not morethan 5000; and has a volume ratio of (inorganic laminarcompound/polyvinyl alcohol) in the range of (5/95) to (30/70).

The present invention further provides a shaped article comprising, atleast a portion thereof, a resin composition; which comprises apolyvinyl alcohol, and an inorganic laminar compound having an aspectratio of not less than 50 and not more than 5000; and has a volume ratioof (inorganic laminar compound/polyvinyl alcohol) in the range of (5/95)to (30/70).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph schematically showing a relationship between an X-raydiffraction peak of an inorganic laminar compound and a “unit thicknessa” of the compound.

FIG. 2 is a graph schematically showing a relationship between an X-raydiffraction peak of a resin composition containing an inorganic laminarcompound and a “lattice spacing (or distance between lattice planes) d”of the composition.

FIG. 3 is a graph schematically showing a relationship between an X-raydiffraction peak of a resin composition and a “lattice spacing d” of thecomposition, in a case where the peak corresponding to the latticespacing d is superposed on halo (or background) and is difficult to bedetected. In this Figure, the area obtained by subtracting a “base line”portion from the peak area in the lower angle side below 2·θ_(d) istreated as the peak corresponding to the “lattice spacing d”.

FIG. 4 is a schematic sectional view showing an embodiment of thelaminate film according to the present invention, which comprises a basematerial, and a layer disposed thereon comprising a resin compositionaccording to the present invention.

FIG. 5 is a schematic sectional view showing another embodiment of thelaminate film according to the present invention, which comprises a basematerial, and a layer disposed thereon comprising a resin compositionaccording to the present invention.

FIG. 6 is a schematic sectional view showing a further embodiment of thelaminate film according to the present invention, which comprises a basematerial, and a layer disposed thereon comprising a resin compositionaccording to the present invention.

FIG. 7 is a schematic sectional view showing a further embodiment of thelaminate film according to the present invention, which comprises a basematerial, and a layer disposed thereon comprising a resin compositionaccording to the present invention.

FIG. 8 is a schematic view for illustrating a folding method used in a“folding test” as described hereinafter.

FIG. 9 (Table 1) is a table showing the structure of laminate filmsobtained in Examples appearing hereinafter.

FIG. 10 (Table 2) is a table showing the data of oxygen permeability,etc., obtained in the above Examples.

FIG. 11 is a graph showing X-ray diffraction peaks of a compositioncomprising a polyvinyl alcohol PVA-117H and “Kunipia F” used inExamples.

FIG. 12 is a graph showing X-ray diffraction peaks of “Kunipia F”(montmorillonite) used in Examples.

FIG. 13 is a graph showing X-ray diffraction peaks of a compositionhaving a lattice spacing d=19.62 angstrom (pattern of the above FIG. 2).

FIG. 14 is a graph showing X-ray diffraction peaks of a compositionhaving a lattice spacing d=32.94 angstrom (pattern having the abovepatterns of FIGS. 2 and 3).

FIG. 15 is a graph showing X-ray diffraction peaks of a compositionhaving a lattice spacing d24 44.13 angstrom (pattern of the above FIG.3).

FIG. 16 is a graph showing X-ray diffraction peaks of a compositionhaving a lattice spacing d≧44.13 angstrom (pattern of the above FIG. 3).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in detail withreference to the accompanying drawings, as desired.

(Polyvinyl Alcohol)

In the present invention, the “polyvinyl alcohol” refers to a polymerpredominantly comprising a monomer unit of vinyl alcohol. Specificexamples of such a “polyvinyl alcohol” may include: a polymer (exactly,a copolymer of vinyl alcohol and vinyl acetate) obtained by subjectingthe acetic acid portion of a vinyl acetate polymer to hydrolysis orester interchange (saponification), and polymers obtained by saponifyinga polymer such as vinyl trifluoroacetate polymer, vinyl formate polymer,vinyl pivalate polymer, t-butyl vinyl ether polymer, and trimethylsilylvinyl ether polymer. With respect to the details of the “polyvinylalcohol”, a book entitled “PVA no Sekai (World of PVA)” edited byPOVAL-KAI (POVAL Society), (1992), published by KOBUNSI KANKO-KAI(Polymer Publishing Society) K.K.; and a book entitled “Poval” writtenby Nagano et al. (1981), published by KOBUNSI KANKO-KAI may be referredto.

The degree of the “saponification” in the polyvinyl alcohol maypreferably be not less than 70% (more preferably, not less than 85%),particularly preferably not less than 98% (i.e., so-called “completelysaponified product”), in terms of mole percentage. The degree ofpolymerization of the polyvinyl alcohol may preferably be not less than100 and not more than 5000 (more preferably, not less than 200 and notmore than 3000).

(Inorganic Laminar Compound)

The “inorganic laminar compound” to be used in the present inventionrefers to an inorganic compound wherein unit crystal layers are mutuallystacked to form a layer structure. In other words, “laminar compound”refers to a compound or substance having a layer structure. The “layerstructure” is a structure wherein planes, each of which comprises atomsstrongly bonded to each other on the basis of covalent bonds, etc., soas to form close packing, are stacked substantially parallel to eachother on the basis of weak bonding power such as Van der Waals force.

The “inorganic laminar compound” usable in the present invention is notparticularly limited, as long as the “aspect ratio” thereof measured bya method described hereinafter is not less than 50 and not more than5000. In view of the gas barrier property, the aspect ratio maypreferably be not less than 100 (particularly, not less than 200).

When the above aspect ratio is less than 50, the exhibition of the gasbarrier property becomes insufficient. On the other hand, it istechnically difficult to obtain an inorganic laminar compound having anaspect ratio exceeding 5000, and further such a compound is costly orexpensive from an economic viewpoint. In view of easiness in productionof an inorganic laminar compound, the aspect ratio may preferably be notmore than 2000 (more preferably, not more than 1500). In view of thebalance between the gas barrier property and the easiness in production,the aspect ratio may preferably be in the range of 200-3000.

In view of the film forming property or formability in the form of afilm or shaped article, the “particle size” measured by a methodtherefor described hereinafter may preferably be not more than 5 μm.When the particle size exceeds 5 μm, the film forming property orformability of a resin composition tends to be decreased. In view of thetransparency of a resin composition, the particle size may morepreferably be not more than 3 μm. In a case where the resin compositionaccording to the present invention is used for a purpose (e.g., purposeof food packaging) wherein the transparency is important, the particlesize may particularly preferably be not more than 1 μm.

Specific examples of the inorganic laminar compound may include:graphite, phosphoric acid salt-type derivative compounds (such aszirconium phosphate-type compound), chalcogen-type compounds, clay-typeminerals, etc. The “chalcogen-type compound” used herein refers to adi-chalcogen type compound which comprises an element of Group IV (Ti,Zr, Hf), Group V (V, Nb, Ta), and/or Group VI (Mo, W), and representedby a formula of MX₂, wherein M denotes an element as described above,and X denotes a chalcogen (S, Se, Te).

In view of easiness in the provision of a large aspect ratio, it ispreferred to use an inorganic laminar compound having a property suchthat it is swollen or cleft in a solvent.

The degree of the “swelling or cleavage” of the inorganic laminarcompound to be used in the present invention in a solvent may beevaluated by the following “swelling or cleavage” test. The inorganiclaminar compound may preferably have a swelling property of not lessthan about 5 (more preferably, not less than about 20) according to thefollowing swelling test. On the other hand, the inorganic laminarcompound may preferably have a cleavage property of not less than about5 (more preferably, not less than about 20) according to the followingcleavage test. In these cases, a solvent having a density smaller thanthe density of the inorganic laminar compound is used. When theinorganic laminar compound is a natural clay mineral having a swellingproperty, it is preferred to use water as the above solvent.

<Swelling Property Test>

2 g of an inorganic laminar compound is slowly added to 100 mL of asolvent, while 100 mL-graduated cylinder is used as a container. Theresultant mixture is left standing, and thereafter the volume of theformer (the dispersion layer of the inorganic laminar compound) is readfrom the graduation corresponding to the interface between thedispersion layer of the inorganic laminar compound and the supernatantafter 24 hours at 23° C. When the resultant value is larger, theswelling property is higher.

<Cleavage Property Test>

30 g of an inorganic laminar compound is slowly added to 1500 mL of asolvent, and is dispersed by means of a dispersion machine (DESPER MH-L,mfd. by Asada Tekko K.K., vane diameter=52 mm, rotating speed=3100 rpm,container capacity=3 L, distance between the bottom face and the vane=28mm) for 90 minutes at a peripheral speed of 8.5 m/sec (23° C.).Thereafter, 100 mL of the resultant dispersion liquid is taken out andplaced into a graduated cylinder, and then is left standing for 60minutes. Then, the volume of the dispersion layer of the inorganiclaminar compound is read from the graduation corresponding to theinterface between the dispersion layer of the inorganic laminar compoundand the supernatant.

As the inorganic laminar compound capable of being swollen or cleft in asolvent, it is particularly preferred to use a clay mineral having aswelling or cleaving property. The clay minerals may be classified intotwo types, i.e., one type having a two-layer structure, which comprisesa silica tetrahedral layer, and an octahedral layer disposed thereon andcomprising a central metal such as aluminum and magnesium; and anothertype having a three-layer structure, which comprises an octahedral layercomprising a central metal such as aluminum and magnesium, and a silicatetrahedral layer disposed on both sides of the octahedral layer so asto sandwich the octahedral layer.

Specific examples of the former two-layer type may include: kaoliniteseries, antigorite series, etc. Specific examples of the latterthree-layer type may include: smectite series, vermiculite series, micaseries, etc., depending on an interlayer cation contained therein.

More specific examples of the clay mineral may include: kaolinite,dickite, nacrite, halloysite, antigorite, chrysotile, pyrophyllite,montmorillonite, hectorite, tetrasilylic mica, sodium taeniolite,muscovite, mercallite or margarosanite, talc, vermiculite, phlogopite,xanthophyllite, chlorite, etc.

(Particle Size)

In view of difficulty, etc., in the measurement of the (true) particlesize in a resin composition, in the present invention, a value (L) whichmay be determined in a solvent by a dynamic light scattering method(photon correlation spectroscopy) as described hereinafter is used asthe “particle size” of the inorganic laminar compound. The “dynamiclight scattering method” used herein is a particle size-measuring methodutilizing a scattering phenomenon of laser light, wherein scatteringlight from particles conducting Brownian movement, i.e., scatteringlight with fluctuation depending on the moving velocity or particle size(grain size) of these particles, is detected, and an information on theparticle size is obtained by calculation.

According to the present inventors' knowledge, the particle size of theinorganic laminar compound contained in a resin may be approximated bythe above-mentioned “particle size in a solvent” obtained by the dynamiclight scattering method. For example, in a case where an inorganiclaminar compound which has sufficiently been swollen with a solvent(which is the same kind of the solvent used in the dynamic lightscattering method) is combined with a resin, the particle size of theinorganic laminar compound contained in the resin may sufficiently beapproximated by the “particle size in a solvent” obtained by the dynamiclight scattering method.

(Aspect Ratio)

In the present invention, the aspect ratio (Z) of the inorganic laminarcompound is a ratio which may be determined on the basis of arelationship of Z=L/a. In this relationship, L is the particle size ofan inorganic laminar compound determined by the dynamic light scatteringmethod in a solvent, and a is the “unit thickness” of the inorganiclaminar compound. The “unit thickness a” is a value which is determinedon the basis of the measurement of the inorganic laminar compound alone,by a powder X-ray diffraction method, etc., as described hereinafter.More specifically, as schematically shown in the graph of FIG. 1 whereinthe abscissa denotes 2·θ, and the ordinate denotes the intensity ofX-ray diffraction peaks, the “unit thickness a” is a spacing obtainedfrom the Bragg's equation (n·λ=2·D·sin θ, n=1, 2, 3 . . . ), wherein θdenotes the angle corresponding to the peak having the lowermost angleamong those of the observed diffraction peaks. With respect to thedetails of the powder X-ray diffraction method, a book entitled“Kiki-Bunseki no Tebiki (Handbook on Instrumental Analysis) (a)”, page69, (1985), editorially supervised by Jiro SHIOKAWA, published by KAGAKUDOJIN K.K. may be referred to.

In correspondence to the above relationship of Z=L/a based on themeasurement of the inorganic laminar compound alone, when the resincomposition according to the present invention is subjected to thepowder X-ray diffraction method, the lattice spacing d of the inorganiclaminar compound contained in the resin composition may usually beobtained.

More specifically, as schematically shown in the graph of FIG. 2 whereinthe abscissa denotes 2·θ, and the ordinate denotes the intensity ofX-ray diffraction peaks, the “lattice spacing d” (a<d) is a spacingcorresponding to the peak having the lowermost angle among the observeddiffraction peaks appearing on the lower angle (larger spacing) side ascompared with the position of the diffraction peak corresponding to theabove-mentioned “unit thickness a”. In a case where the above peakcorresponding to the “lattice spacing d” is superposed on a halo (orbackground) as schematically shown in the graph of FIG. 3 so that it isdifficult to detect such a peak, the area of a portion obtained bysubtracting the base line portion from a portion corresponding to anangle lower than 2·θ_(d), is treated as a peak corresponding to the“lattice spacing d”. The θ_(d) used herein is an angle of diffractioncorresponding to “(unit length a)+(width of one resin chain)”. Withrespect to the details of a method of determining the “lattice spacingd”, a book entitled “Nendo no Jiten (Encyclopedia of Clay)”, page 35 etseq. and page 271 et seq., (1985), edited by Shuici IWAO et al.,published by ASAKURA SHOTEN K.K. may be referred to.

The integrated intensity of the diffraction peak (corresponding to the“lattice spacing d”) observed in the powder X-ray diffraction of a resincomposition may preferably have a relative ratio of not less than 2(more preferably, not less than 10), with respect to the integratedintensity of the diffraction peak as a standard (corresponding to the“lattice spacing a”).

In general, the difference between the above lattice spacing d and the“unit thickness a”, namely, the value of k=(d−a) (when converted into“length”) may be equal to, or larger than the width of one resin chainconstituting the resin composition (k=(d−a)≧(width of one resin chain)).The “width of one resin chain” may be determined by simulationcalculation, etc. (as described in, e.g., a book entitled “KOBUNSHIKAGAKU JORON (Introduction to Polymer Chemistry)”, pages 103-110 (1981),published by KAGAKU DOJIN K.K.). In the case of polyvinyl alcohol, thiswidth is 4-5 Å (angstrom), and in the case of water molecules, thiswidth is 2-3Å.

It is considered that the above-mentioned aspect ratio Z=L/a is notalways equal to “true aspect ratio” of the inorganic laminar compound inthe resin composition. However, it is reasonable to approximate the“true aspect ratio” by the aspect ratio Z, for the following reason.

Thus, it is extremely difficult to directly measure the “true aspectratio” of the inorganic laminar compound contained in a resincomposition. On the other hand, in a case where there is a relationshipof a<d between the lattice spacing d determined-by the powder X-raydiffraction method for the resin composition, and the “unit thickness a”determined by the powder X-ray diffraction method for the inorganiclaminar compound alone; and the value of (d−a) is not smaller than thewidth of one resin chain in the resin composition, it is assumed thatthe resin is inserted between layers of the inorganic laminar compound.Accordingly, it is sufficiently reasonable to approximate the thicknessof the inorganic laminar compound in the resin composition by theabove-mentioned “unit thickness a”, i.e., to approximate the “trueaspect ratio” in the resin composition by the above-mentioned “aspectratio Z” of the inorganic laminar compound alone.

As described above, it is extremely difficult to measure the trueparticle size in the resin composition. However, it may be consideredthat the particle size of the inorganic laminar compound in the resin isquite near to the particle size in a solvent, when the inorganic laminarcompound, which has fully been swollen with a solvent of the same kindas that of the solvent used in the dynamic light scattering method, iscombined with a resin to provide a resin composition. However, it ishardly considered that the particle size L determined by the dynamiclight scattering method exceeds the major axis length L_(max) of theinorganic laminar compound, and therefore the possibility that trueaspect ratio (L_(max)/a) is smaller than the “aspect ratio Z” used inthe present invention (i.e., the possibility of L_(max)/a<Z), istheoretically very small.

In consideration of the above-mentioned two viewpoints, it is consideredthat the definition of the aspect ratio Z used in the present inventionis sufficiently reasonable. Thus, in the present specification, the“aspect ratio” or “particle size” means the “aspect ratio Z” as definedabove, or “particle size L” determined by the dynamic light scatteringmethod.

(Solvent)

In the present invention, the solvent for swelling the inorganic laminarcompound is not particularly limited, as long as it is usable in theproduction of the resin composition. For example, when a natural claymineral having a swelling property is used as an inorganic laminarcompound, specific examples of the solvent may include: water, alcoholssuch as methanol; polar solvent such as dimethylformamide, dimethylsulfoxide, and acetone; or mixtures comprising two or more speciesselected from these solvents. It is preferred to use water or an alcoholsuch as methanol having a relatively low boiling point, in view ofeasiness in the removal thereof after the film formation or shaping ofthe resin composition.

(Crosslinking Agent for Hydrogen-bonding Group)

In the present invention, a crosslinking agent for a hydrogen-bondinggroup (such as hydroxyl group) may be used as desired, for the purposeof improving the water resistance (or barrier property afterwater-resistance environmental test) of a highly hydrogen-bonding resinsuch as polyvinyl alcohol.

The crosslinking agent for the hydrogen-bonding group usable in thepresent invention is not particularly limited. Preferred examples of thecrosslinking agent may include: titanium-type coupling agent,silane-type coupling agent, melamine-type coupling agent, epoxy-typecoupling agent, isocyanate-type coupling agent, copper compound,zirconia compound, etc. In view of the water resistance, a zirconiacompound may particularly preferably be used.

Specific examples of the zirconia compound may include: halogenatedzirconium such as zirconium oxychloride, hydroxy zirconium chloride,zirconium tetrachloride, and zirconium bromide; zirconium salts ofmineral acid such as zirconium sulfate, basic zirconium sulfate, andzirconium nitrate; zirconium salts of organic acid such as zirconiumformate, zirconium acetate, zirconium propionate, zirconium caprylate,and zirconium stearate; zirconium complex salts such as zirconiumammonium carbonate, zirconium sodium sulfate, zirconium ammoniumacetate, zirconium sodium oxalate, zirconium sodium citrate, zirconiumammonium citrate; etc.

The amount of the addition of the crosslinking agent for ahydrogen-bonding group is not particularly limited, but the crosslinkingagent may preferably be used so as to provide a ratio (K=CN/HN), i.e.,ratio of the mole (CN) of the crosslinking-providing group of thecrosslinking agent, to the mole (HN) of the hydrogen-bonding group ofthe highly hydrogen-bonding resin (such as polyvinyl alcohol), which isnot less than 0.001 and not more than 10. The above molar ratio K maymore preferably be in the range of not less than 0.01 and not more than1.

(Transparency)

A film or shaped article comprising the resin composition according tothe present invention may preferably have a transparency, in view ofadvantage in a case where it is used for a purpose such as packaging.The transparency may preferably have a degree of not less than 80% (morepreferably, not less than %) in terms of transmittance of whole light ata wavelength of 500 nm. For example, such a transparency may preferablybe measured by means of a commercially available spectrophotometer(Automatic Recording Spectrophotometer Model-330, mfd. by HitachiSeisakusho K.K.)

(Oxygen Permeability)

The resin composition, laminate, or laminate film according to thepresent invention has a gas barrier property. The gas barrier propertymay preferably be not more than 0.5 cc/m²·day·atm, more preferably, notmore than 0.2 cc/m²·day·atm (particularly preferably, not more than 0.15cc/m²·day·atm), in terms of an oxygen permeability under the conditionsof 30° C. and 60% RH (relative humidity).

(Resistance to Folding)

The resin composition, laminate or laminate film according to thepresent invention may preferably have a folding (or bending) resistance.The folding resistance may preferably be 100 or less, more preferably 20or less (particularly preferably, 10 or less), in terms of an incrementratio R in the oxygen permeability defined by R=P_(F)/P_(I) (whereinP_(F) denotes the oxygen permeability after a folding test, and P_(I)denotes the oxygen permeability before the folding test), when the resincomposition, laminate, or laminate film according to the presentinvention is subjected to a “folding test” as described hereinafter. Atthe time of the folding test, the resin composition is subjected to thefolding test, after a layer comprising the resin composition and havinga thickness after drying of 0.8 μm is formed on a 20 μm-thick “OPP Film”as described hereinafter so that the entirety thereof is formed into alaminated film-type shape.

(Resin Composition)

With respect to the composition ratio (volume ratio) between theinorganic laminar compound and the polyvinyl alcohol used in the presentinvention, the volume ratio of inorganic laminar compound/polyvinylalcohol (ratio at the time of “Shikomi” (mixing for preparation)) is inthe range of 5/95 to 30/70. When the volume ratio (volume fraction) ofthe above inorganic laminar compound/polyvinyl alcohol is below 5/95,the gas barrier property becomes insufficient, and particularly, thedecrease in the barrier property due to folding becomes marked. On theother hand, when the above volume ratio exceeds 30/70, the resultantflexibility or formability of the film becomes insufficient, wherebypeeling from a base material is liable to occur in the case of alaminate film.

In view of the suppression of a decrease in the barrier property due tofolding, the volume ratio may preferably be not less than 7/93. On theother hand, in view of the flexibility or the suppression of peelingproperty from the base material, the volume ratio may preferably be notmore than 17/83. In other words, a volume ratio in the range of 7/93 to17/83 is particularly preferred, because the decrease in the barrierproperty due to the folding may substantially be obviated, and a highbarrier property may easily be obtained in such a range.

Such a volume ratio may be determined by dividing respectively thenumerator value (weight of the inorganic laminar compound) and thedenominator value (weight of resin) constituting the weight ratio at thetime of the “mixing for preparation” of these components, by respectivedensities. In general, there can be a case wherein the density of aresin (e.g., polyvinyl alcohol) is somewhat different depending on thecrystallinity thereof. In the above case, however, it is possible tocalculate the volume ratio while assuming the crystallinity of thepolyvinyl alcohol to be 50%

(Production Method)

The method of formulating or producing the above composition comprisingan inorganic laminar compound and a polyvinyl alcohol is notparticularly limited. In view of the homogeneity or easiness in handlingat the time of the formulation, it is possible to adopt, e.g., a method(first method) wherein a solution obtained by dissolving a polyvinylalcohol, and a dispersion obtained by preliminarily swelling or cleavingan inorganic laminar compound, are mixed with each other, and thereafterthe solvent is removed; a method (second method) wherein a dispersionobtained by swelling or cleaving an inorganic laminar compound, is addedto a polyvinyl alcohol, and thereafter the solvent is removed; a method(third method) wherein an inorganic laminar compound is added to asolution obtained by dissolving a polyvinyl alcohol to obtain adispersion in which the inorganic laminar compound is swollen or cleft,and thereafter the solvent is removed; a method (fourth method) whereinan inorganic laminar compound and a polyvinyl alcohol are kneaded underheating; etc. In view of easiness in the provision of a large aspectratio of the inorganic laminar compound, it is preferred to adopt theformer three method (first to third methods).

In the former two methods (first to second methods), in view ofimprovement in the water resistance (barrier property after thewater-resistance environmental test), it is preferred that the solventis removed from the system and thereafter a thermal aging treatment isconducted at a temperature of not less than 110° C. and not more than220° C. (more preferably, a temperature of not less than 130° C. and notmore than 210° C.). The aging period of time is not particularlylimited. In consideration of the necessity for a film temperature toreach at least a set temperature, for example, it is preferred to adoptan aging time of not less than 1 sec. and not more than 100 min. (morepreferably, about 3 sec. to 10 min.) in the case of a drying methodusing a heating medium contact type dryer such as hot-air dryer, in viewof a balance between the water resistance and productivity.

The heat source to be used in the above aging treatment is notparticularly limited. For example, it is possible to apply any ofvarious methods such as those utilizing heat roll contact, heat mediumcontact (air, oil, etc.), infrared heating, and microwave heating.

The effect of improving the water resistance may remarkably be enhancedin a case where the inorganic laminar compound is a clay mineral havinga swelling property.

(Laminate Structure)

The laminate structure or shaped structure of a resin compositionaccording to the present invention is not particularly limited, as longas it comprise, as at least a portion (or layer) thereof, a polyvinylalcohol composition comprising a polyvinyl alcohol and an inorganiclaminar compound having an aspect ratio of not less than 50 and not morethan 5000. More specifically, the resin composition according to thepresent invention may be shaped into any of various forms such as film,sheet, and container.

FIG. 4 is a schematic sectional view showing an embodiment wherein theresin composition according to the present invention is shaped into theform of a laminate film. Referring to FIG. 4, the laminate film in thisembodiment comprises a first base material layer 2, and a layer 1 of aresin composition disposed thereon comprising an inorganic laminarcompound and a polyvinyl alcohol.

The laminate film according to the present invention may also have alaminate structure as shown in the schematic sectional views of FIGS.5-7. The laminate film in the embodiment of FIG. 5 comprises a secondbase material layer 3, a first base material layer 2 disposed on thesecond base material layer 3, and a layer 1 of a resin compositiondisposed on the first base material layer 2 and comprising an inorganiclaminar compound and a polyvinyl alcohol. The laminate film in theembodiment of FIG. 6 comprises a first base material layer 2, a layer 1of a resin composition disposed on the first base material layer 2 andcomprising an inorganic laminar compound and a polyvinyl alcohol, and asecond base material layer 3 disposed on the resin composition layer 1.In addition, the laminate film in the embodiment of FIG. 7 comprises asecond base material layer 3, a first base material layer 2 disposed onthe second base material layer 3, a layer 1 of a resin compositiondisposed on the first base material layer 2 and comprising an inorganiclaminar compound and a polyvinyl alcohol, and a second base materiallayer 3 a disposed on the resin composition layer 1.

(Base Material)

In the present invention, the base material to be used for the basematerial (or substrate) layer (e.g., the base material layer 2 in theembodiment of FIG. 4) is not particularly limited. It is possible to useany of known or ordinary base materials such as resin, paper, aluminumfoil, woody material, cloth, and nonwoven fabric, in accordance with theuse or purpose thereof.

Specific examples of the polyvinyl alcohol constituting the basematerial may include: polyolefin-type resins such as polyethylene (lowdensity, high density) ethylene-propylene copolymer, ethylene-butenecopolymer, ethylene-hexene copolymer, ethylene-octene copolymer,polypropylene, ethylene-vinyl acetate copolymer, ethylene-methylmethacrylate copolymer, and ionomer resin; polyester-type resins such aspolyethylene terephthalate (PET), polybutylene terephthalate, andpolyethylene naphthalate; amide-type resins such as nylon-6, nylon-6·6,meta-xylenediamine-adipic acid condensation polymer, and polymethylmethacrylimide; acrylic-type resins such as polymethyl methacrylate;styrene- or acrylonitrile-type resins such as polystyrene,styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadienecopolymer, and polyacrylonitrile; hydrophobicity-imparted cellulose-typeresins such as cellulose triacetate, and cellulose diacetate;halogen-containing resins such as polyvinyl chloride, polyvinylidenechloride, polyvinylidene fluoride, and polytetrafluoroethylene (Teflon);hydrogen-bonding resins such as polyvinyl alcohol, ethylene-vinylalcohol copolymer and cellulose derivatives; engineering plastic-typeresins such as polycarbonate polyvinyl alcohol, polysulfone resin,polyethersulfone resin, polyether ether ketone resin, polyphenyleneoxide resin, polymethylene oxide resin, and liquid crystal resin; etc.

In the present invention, in view of the strength or gloss, the resinlayer to be used for the above-mentioned base material layer maypreferably be an oriented (particularly, biaxially oriented) film.Specific examples of such an oriented film may include a biaxiallyoriented polypropylene film, a biaxially oriented polyamide film, abiaxially oriented polyethylene terephthalate film, etc.

(Method of Forming Lamination, etc.)

The method for laminating or forming a laminate or laminate film is notparticularly limited. As a method for laminating a resin compositionlayer containing an inorganic laminar compound on a base material layer,it is preferred to use a coating method wherein a coating liquidcontaining a composition comprising a polyvinyl alcohol and an inorganiclaminar compound is applied onto the surface of a base material, andthen dried and heat-treated; a method wherein a layer of a resincomposition containing an inorganic laminar compound is laminatedafterward onto a base material layer; a method wherein a resin(forforming a base material layer) is extrusion-laminated onto a resincomposition layer containing an inorganic laminar compound; etc. One ormore interfaces between the respective layers constituting the laminatefilm according to the present invention may be subjected to a treatmentsuch as corona treatment and anchor coating treatment, as desired.

Specific examples of the coating method may include: gravure methodssuch as direct gravure method, reverse gravure method and micro-gravuremethod; roll coating methods such as twin-roll bead coating method, andbottom-feed triple reverse coating method; doctor knife method, diecoating method, dip coating method, bar coating method, and coatingmethod combining these coating methods.

When the above-mentioned laminate is formed, it is preferred to use amethod wherein an inorganic laminar compound, which is in a state suchthat it has been swollen or cleft in a solvent, is dispersed in apolyvinyl alcohol resin (or a solution of such a resin), and then thesolvent is removed from the resultant mixture system while substantiallyretaining such a dispersion state.

The thickness of a layer comprising a resin composition comprising aninorganic laminar compound and a polyvinyl alcohol is not particularlylimited. While the thickness of the resin composition layer is somewhatdifferent depending on the kind of a base material to be combinedtherewith, or an intended barrier performance, etc., the thickness maypreferably be not more than 10 μm in terms of the thickness afterdrying. In a case where a higher transparency is demanded, the thicknessmay preferably be not more than 2 μm (more preferably, not more than 1μm) in terms of thickness after drying. When the thickness is not morethan 1 μm, it is considerably advantageous in view of the transparencyas the resultant laminate. Accordingly, such a thickness is particularlypreferred for a use wherein transparency is particularly demanded (e.g.,use for food packaging).

The thickness of the resin composition layer does not have a particularlower limit. In view of provision of a sufficient gas barrier property,the thickness may preferably be 1 nm or larger, more preferably 10 nm orlarger (particularly preferably, 100 nm or larger).

In the present invention, it is possible to laminate another basematerial (such as the second base material 3 or 3 a in the embodimentsof FIGS. 5-6) onto the above-mentioned laminate film comprising a firstbase material and a resin composition layer. The base material to beused for such a purpose is not particularly limited, and mayappropriately be selected in accordance with the use or purpose thereof.For example, it is possible to use any of known or ordinary basematerials such as resin, paper, aluminum foil, woody material, cloth,and nonwoven fabric as described hereinabove.

In addition, it is also possible to mix with or add to the resincomposition, film or shaped article according to the present inventionas desired, any of various additives such as ultraviolet light absorbingagent, colorant, and antioxidant, within a range wherein the effect ofthe present invention is not substantially impaired. Further, it is ofcourse possible to use an adhesive or printing ink, as desired, e.g., atthe time of laminating operation.

Hereinbelow, the present invention will be described in detail withreference to Examples, by which the present invention is not limited.

EXAMPLES

The methods of measuring various physical properties used in the presentspecification are described below.

<Oxygen Permeability>

Oxygen permeability was measured by using a method according to JapaneseIndustrial Standard (JIS) (JIS K-7126).

More specifically, a sample film (test piece) was mounted to acommercially available oxygen permeability measuring apparatus (tradename: OX-TRAN 10/50A, mfd. by MOCON Co. U.S.A.), and the oxygenpermeability was measured under the measuring conditions of atemperature of 31° C. (humidity-controlled thermostat=21° C.). At thistime, the relative humidity was about 61%. In this measurement, theoxygen permeability of the sample film was continuously measured, andthe oxygen permeability at a point of time at which the oxygenpermeability became substantially constant (usually, about several hoursto three days after the initiation of the measurement) was used as thedata thereof in this specification. When the oxygen transmission isrepresented by the ordinate of a graph, and the time t is represented bythe abscissa thereof, the period of time (θ sec.) wherein the filminterior reaches the equilibrium may be represented by an equation ofθ=d²/6·D, wherein d denotes the film thickness (μm) of the sample film,and D denotes a diffusion constant ((μm)²/sec). Accordingly, the periodof time for the measurement is different depending on the kind of thesample.

<Folding Test>

A 33 cm-wide non-oriented polypropylene film (trade name: PyleneFilm-CT, mfd. by Toyobo K.K., thickness 50 μm) was dry-laminated onto aninorganic laminar compound-containing layer (resin composition layer)side of a laminate film to be examined by means of a laminating machine(trade name: Test-Coater, mfd. by Yasui Seiki co.) under a pressure of 4kg/cm at a speed of 6 m/min., while using a urethane-type adhesive(trade name: Yunoflex-J3, mfd. by Sanyo Kasei K.K.) in an amount of 3g/m² (solid content). The resultant dry-laminated film was then sampledto be formed into a test piece form having a length of 12 cm and a widthof 12 cm.

The test piece was subjected to “folding” in the following manner. Thus,as shown in FIG. 8, the test piece (Step 1) was folded into anaccordion-like shape having an interval of 1 cm by using hands (Step 2).The resultant test piece was then sandwiched between two flat plates ofacrylic resin (dimensions: 15 cm×15 cm, thickness: about 5 mm). A loadof 5 kg was applied to the resultant sandwich-like product, and thesandwich-like product was left standing for 30 min. in this state (Step3). Then, the application of the load was removed and the test piece wasonce spread (Step 4). Thereafter, the spread test piece was againsubjected to the above “folding” process (Steps 2 to 3) except that thetest piece was provided with folds perpendicular to the “first folds”which had been provided to the test piece as described above, to befolded into an accordion-like shape having an interval of 1 cm, wherebya “test piece after folding” (Step 5) was obtained.

The thus prepared “test piece after folding” was subjected to oxygenpermeability measurement in a manner as described hereinabove. Whenpin-holes, etc., are formed in the inorganic laminar compound-containinglayer during the above “folding”, the resultant oxygen permeabilitytends to be increased.

<Film Strength Test (Qualitative Test)>

A double-side coated adhesive tape was bonded to a test piece (length 5cm×5 cm square) of a laminate film to be examined on the oppositesurface side thereof, which is the side opposite to the inorganiclaminar compound-containing layer (resin composition layer), and thenthe test piece was fixed onto a flat plate of acrylic resin. One cuttingline having a dimension of 5 mm×5 mm square was imparted to the thusfixed test piece by use of a cutter knife. Then, a commerciallyavailable adhesive cellophane tape (trade name: Sekisui-Celotape, mfd.by Sekisui Kagaku Kogyo K.K., width: 18 mm) was bonded to the test piecein a length of about 3 cm so as to cover the above-mentioned “cuttingline” under a load of 1 kg/cm² for 10 min. Thereafter, the above acrylicresin plate and the adhesive cellophane tape were peeled from each otherby hands so as to provide an angle of about 90 degrees therebetween,whereby the breakage or peeling of the inorganic laminarcompound-containing layer was observed with naked eyes.

As a result of the above peeling test, a case wherein the breakage orpeeling of the inorganic laminar compound-containing layer was observedwas represented by a symbol “×” and a case wherein no breakage orpeeling of the inorganic laminar compound-containing layer was observedwas represented by a symbol “◯”.

<Thickness Measurement>

A thickness of not less than 0.5 μm was measured by means of acommercially available digital-type thickness measuring device(contact-type thickness measuring device, trade name: Ultra-HighPrecision Deci-Micro Head MH-15M, mfd. by Nihon Kogaku Co.).

On the other hand, a thickness of less than 0.5 μm was determined by agravimetric analysis method, wherein the weight of a film having apredetermined area was measured, the resultant weight was divided by thearea, and further divided by the specific gravity of the composition; oran elemental analysis method (in the case of a laminate comprising aresin composition layer and a base material, etc.).

In a case where the elemental analysis (measuring principle: ICPemission spectrometry, with reference to a book entitled “ICP EmissionSpectrometry”, edited by Nihon Bunseki Kagaku-kai (Japan Society ofAnalytical Chemistry), 1988, published by Kyoritsu Shuppan) was used,the ratio between the layer of the resin composition according to thepresent invention and the base material was determined by calculation onthe basis of the ratio between the analytical value of a predeterminedinorganic element (originating from the composition) of the laminate,and the fraction of a predetermined element (e.g., Si) of the inorganiclaminar compound alone.

<Particle Size Measurement>

Predetermined parameters such as the refractive index of a solvent(e.g., n=1.332 in the case of water), the viscosity of the solvent(e.g., n=0.890 cP, in the case of water), and the refractive index of aninorganic laminar compound (e.g., n=1.56 in the case of mica) wereinputted to a commercially available ultrafine particle size analyzingapparatus (trade name: BI-90, mfd. by Brookheaven Co., U.S.A., Japaneseagent: Nikkiso K.K.), and measurement was conducted at a temperature of25° C., in a solvent of water, while a solution having a weight ratio(inorganic laminar compound/water) of 2% was diluted in accordance withan estimated particle size. Through such a method, the particle size Lwas determined as a central particle size value measured by a photoncorrelation method based on dynamic light scattering, which wasautomatically outputted from the above analyzer as a digital value. Inthis particle size measurement for the inorganic laminar compound, eachtime the measurement was conducted, calibration measurement was alsoconducted by using the following standard samples comprising truespherical fine particles, whereby it was confirmed that the measureddata of the particle size of the standard samples fell within the rangeof relative error of ±10%.

True Spherical Fine Particles: particles mfd. by Dow Chemical Co.,U.S.A., trade name: UNIFORM LATEX PARTICLES

<Particle Sizes Determined by SEM (Scanning Electron Microscope); Dow>

0.085 μm (deviation 0.0055 μm)

0.109 μm (deviation 0.0027 μm)

0.330 μm (deviation 0.0040 μm)

0.806 μm (deviation 0.0057 μm)

2.02 μm (deviation 0.0135 μm)

2.97 μm (deviation 0.23 μm)

<Aspect Ratio Calculation>

An inorganic laminar compound and a resin composition were respectivelysubjected to diffraction measurement by means of a commerciallyavailable X-ray diffractometer (trade name: XD-5A, mfd. by ShimazuSeisakusho K.K.) through a powder method. The lattice spacing (unitthickness) a was determined on the basis of the measurement of theinorganic laminar compound alone. In addition, it was confirmed that aportion in which the lattice spacing of the inorganic laminar compoundhad been increased (a portion in which lattice spacing d>a) was presentin the resin composition, on the basis of the diffraction measurement ofthe resin composition.

By use of the resultant particle size L obtained by the dynamicscattering method, the aspect ratio Z was determined by using anequation of Z=L/a.

Example 1

Natural montmorillonite (trade name: Kunipia F, mfd. by Kunimine KogyoK.K.) was dispersed in ion-exchange water (electric conductivity: 0.7μS/cm or below) so as to provide a concentration of 1 wt. %, thereby toprovide a dispersion of an inorganic laminar compound (Liquid A). Theabove montmorillonite had a particle size of 560 nm, a unit thickness aobtained by powder X-ray diffraction of 1.2156 nm, and an aspect ratioof 461.

Separately, a polyvinyl alcohol (trade name: PVA 117H, mfd. by KurarayK.K., saponification degree=99.6%, degree of polymerization=1700) wasdissolved in ion-exchange water (electric conductivity: 0.7 μS/cm orbelow) so as to provide a concentration of 1 wt. %, thereby to provide aresin solution (Liquid B).

The thus obtained Liquids A and B were mixed with each other so as toprovide a solid content ratio (volume ratio) of (inorganic laminarcompound/resin)=5.3/94.7, thereby to provide a coating liquid.

A 20 μm-thick biaxially oriented polypropylene film (trade name: PyleneFilm OT, mfd. by Toyobo K.K.) was subjected to corona dischargetreatment. Onto the thus treated film, the coating liquid having theabove composition was applied by gravure coating (by use of “TestCoater” mfd. by Yasui Seiki K.K., microgravure coating method, coatingspeed: 3 m/min., drying temperature: 80° C. (inlet side heater), 100° C.(outlet side heater)), thereby to provide a laminate film. The thicknessafter drying of the above coating layer was 0.8 μm.

The thus obtained laminate film was subjected to an oxygen permeabilitytest, a folding test, and a film strength test. The test results areshown in FIG. 10 (Table 2).

As shown in the above Table 2, the laminate film obtained by thisexample provided excellent results with respect to all of the items ofthe above oxygen permeability, folding resistance (suppression of adecrease in barrier property due to folding), and film strength.

Examples 2-7

Laminate films were prepared and were subjected to an oxygenpermeability test, a folding test, and a film strength test in the samemanner as in Example 1, except that the kind of the base material orinorganic laminar compound, and the volume ratio between the inorganiclaminar compound and the polyvinyl alcohol were respectively changed tothose shown in Table 1 (FIG. 9). The test results are shown in Table 2(FIG. 10).

As shown in the above Table 2, the laminate films obtained by theseexamples provided excellent results with respect to all of the items ofthe above oxygen permeability, folding resistance (suppression of adecrease in barrier property due to folding), and film strength.

Example 8

Zirconium ammonium carbonate (trade name: Zircozol AC7, mfd. by Dai-ichiKigenso Kogyo K.K., an aqueous solution containing 15 wt. % of thesolute (calculated in terms of zirconium oxide)), as a crosslinkingagent for hydrogen-bonding group was added to the mixture solutioncomprising the Liquid A and Liquid B prepared in Example 1 in an amountso as to provide a ratio of the zirconium element of one mole, withrespect to 15 mole of the hydroxyl group of the polyvinyl alcohol. Byuse of the resultant mixture, a laminate film was prepared and wassubjected to an oxygen permeability test, and a film strength test inthe same manner as in Example 1, except that a biaxially orientedpolyethylene terephthalate film (trade name: Lumilar, mfd. by TorayK.K., thickness: 25 μm) was used as the base material, and the otherconstituents were changed to those as shown in Table 1 (FIG. 9). Therespective measurement results are shown in the above Table 2 (FIG. 10).

As shown in the above Table 2, the laminate film obtained by thisexample provided excellent results with respect to all of the items ofthe above oxygen permeability, and film strength.

Example 9

Zirconium ammonium carbonate (trade name: Zircozol AC7, mfd. by Dai-ichiKigenso Kogyo K.K., an aqueous solution containing 15 wt. % of thesolute (calculated in terms of zirconium oxide)), as a crosslinkingagent for hydrogen-bonding group was added to the mixture solutioncomprising Liquid A and Liquid B prepared in Example 1 in an amount soas to provide a ratio of the zirconium element of one mole with respectto 15 mole of the hydroxyl group the polyvinyl alcohol. By use of theresultant mixture, a laminate film was prepared in the same manner as inExample 1, except that the other constituents were changed to those asshown in Table 1 (FIG. 9). Thereafter, the resultant laminate film wassubjected to a heat treatment by means of a hot-air dryer at 180° C. for5 min., thereby to provide a laminate film.

The thus prepared laminate film was subjected to an oxygen permeabilitytest and a film strength test. The respective measurement results areshown in the above Table 2 (FIG. 10). As shown in the above Table 2, thelaminate film obtained by this example was excellent in both of theabove oxygen permeability and film strength.

Comparative Examples 1-2

Laminate films were prepared and were subjected to an oxygenpermeability test, a folding test, and a film strength test in the samemanner as in Example 1, except that an inorganic laminar compound havinga small aspect ratio (aspect ratio Z=about 35) was used and the otherconstituents were changed to those as shown in Table 1 (FIG. 9). Thetest results are shown in Table 2 (FIG. 10).

As shown in the above Table 2, the laminate films obtained by theseComparative Examples were considerably poor in the gas barrier property.

Comparative Example 3

A laminate films was prepared and was subjected to an oxygenpermeability test, a folding test, and a film strength test in the samemanner as in Example 1, except that the volume ratio between theinorganic laminar compound and the polyvinyl alcohol was changed to thatas shown in Table 1 (FIG. 9). The test results are shown in Table 2(FIG. 10).

As shown in the above Table 2, the laminate film obtained by thisComparative Example was considerably poor in the folding resistance, andwas also weak in the film strength.

Comparative Example 4

A laminate films was prepared and was subjected to an oxygenpermeability test, a folding test, and a film strength test in the samemanner as in Example 1, except that the inorganic laminar compound wasused without adding a polyvinyl alcohol thereto (i.e., volume ratio ofthe inorganic laminar compound=0) as shown in Table 1 (FIG. 9). The testresults are shown in Table 2 (FIG. 10).

As shown in the above Table 2, the laminate film obtained by thisComparative Example was considerably poor in the gas barrier property.

Comparative Example 5

A laminate films was prepared and was subjected to an oxygenpermeability test, a folding test, and a film strength test in the samemanner as in Example 9, except that the kind of the inorganic laminarcompound, the volume ratio between the inorganic laminar compound andthe polyvinyl alcohol, and the crosslinking agent for hydrogen-bondinggroup were changed to those as shown in Table 1 (FIG. 9). The testresults are shown in Table 2 (FIG. 10).

As shown in the above Table 2, the laminate film obtained by thisComparative Example was weak in the film strength.

Comparative Example 6

The oxygen permeability of a commercially available 20 μm-thickbiaxially oriented polypropylene film (trade name: Pylene Film-OT, mfd.by Toyobo K.K.) was measured. As a result, it was found that the oxygenpermeability was not less than 1000 cc/m²·day·atm, and the film wasconsiderably poor in the gas barrier property.

The meanings of the abbreviation used in the above Table 1 (FIG. 9) areas follows.

CPP: Polypropylene film (trade name: Pylene Film-CT, mfd. by ToyoboK.K.)

OPP: Biaxially oriented polypropylene film (trade name: Pylene Film-OT,mfd. by Toyobo K.K.)

OPET: Biaxially oriented polyethylene terephthalate film (trade name:Lumilar, mfd. by Toray K.K.)

NA: Tetrasilylic mica fine powder (trade name: NaTS, mfd. by Topee KogyoCo.); particle size=977 nm, unit thickness a=0.9557 nm, aspect ratioZ=1043.

F: Natural montmorillonite (trade name: Kunipia F, mfd. by KunimineKogyo Co.); particle size=560 nm, unit thickness a=1.2156 nm, aspectratio Z=461.

L: Synthetic hectorite (trade name: Laponite XLS, mfd. by Nihon SilicaKogyo Co.); particle size=35 nm, unit thickness a=about 1 nm(diffraction peak was broad), aspect ratio Z=about 35.

H: Polyvinyl alcohol (trade name: Poval 117H, mfd. by Kuraray K.K.,degree of polymerization=1700, saponification degree=99.6 mol %,)

117: Polyvinyl alcohol (trade name: Poval 117, mfd. by Kuraray K.K.,degree of polymerization=1700, saponification degree=98.5 mol %)

Z: Aqueous solution of zirconium ammonium carbonate (trade name:Zircozol AC7, mfd. by Dai-ichi Kigenso Kogyo Co.)

A: Heat treatment at 180° C., for 5 min.

FIGS. 11-16 respectively show powder X-ray diffraction peaks of aninorganic laminar compound or composition each having various values ofthe lattice spacing d.

FIG. 11 is a graph showing X-ray diffraction peaks of a polyvinylalcohol PVA-117H/“Kunipia F” composition used in the above Examples.FIG. 12 is a graph showing X-ray diffraction peaks of “Kunipia F”(montmorillonite) used in the above Examples.

FIG. 13 (composition having a lattice spacing d=19.62 Å (pattern of theabove FIG. 2), FIG. 14 (composition having a lattice spacing d=32.94 Å,pattern of the above FIG. 2 or FIG. 3), FIG. 15 (composition having alattice spacing d≧44.13 Å, pattern of the above FIG. 3), and FIG. 16(composition having a lattice spacing d≧44.13 Å, pattern of the aboveFIG. 3) are graphs respectively showing powder X-ray diffraction peaksof compositions having various values of the lattice spacing d.

INDUSTRIAL APPLICABILITY

As described hereinabove, according to the present invention, there areprovided a resin composition comprising: polyvinyl alcohol, and aninorganic laminar compound having an aspect ratio of not less than 50and not more than 5000, wherein the volume ratio of (inorganic laminarcompound/polyvinyl alcohol) is in the range of (5/95) to (30/70); alaminate comprising such a resin composition as at least a layerthereof; and a laminate film comprising a base material and at least onelayer disposed thereon and comprising the above resin composition.

According to the present invention, a gas barrier property at a highlevel which has never been achieved in the prior art, may be imparted tothe resin composition, while retaining both of a good folding resistanceand a good film strength.

As described in the above “Best Mode for Carrying Out the invention” and“Examples”, although an inorganic laminar compound having a small aspectratio imparts only a low gas barrier property to a polyvinyl alcohol, aninorganic laminar compound having an aspect ratio of not less than 50and not more than 5000 used in the present invention exhibit asufficient effect of imparting a gas barrier property to a polyvinylalcohol. In addition, in the above volume ratio (inorganic laminarcompound/polyvinyl alcohol) range of (5/95) to (30/70) used in thepresent invention, i.e., in a relatively small volume fraction range ofthe inorganic laminar compound, a pin hole which is capable ofconsiderably decreasing the gas barrier property at the time of foldingis less liable to be produced. As a result, in such a range, thedropping-out of a film comprising the above resin composition iseffectively suppressed, and further the peeling strength at the time oflaminating an inorganic laminar compound-containing layer onto anotherbase material may be considerably improved.

On the basis of the above-mentioned characteristics, the resincomposition, or laminate film according to the present invention isusable as a packaging material. In the usage in food packaging, it isusable for a wide range of packaging, such as: “miso” (soybean paste),pickles, daily dish, baby food, “tsukudani” (preserved food boiled downin soy sauce), “konnyaku” (paste made from devil's-tongue), “chikuwa”(Japanese fish paste cooked in a bamboo-like shape), “kamaboko” (boiledfish paste), processed marine products, meat ball, hamburger steak,Genghis Khan-type meat (meat for cooking), ham, sausage, and otherprocessed stock raising products, green tea, coffee, tea, dried bonito,“tororo-konbu” (sliced tangle), oily confectionery such as French friedpotatoes and buttered peanuts, confectionery made from rice, biscuit,cookie, cake, “manjuu” (bun stuffed with sweetened bean paste), spongecake, cheese, butter, cut rice cake, soup, source, Chinese noodles, etc.

In addition, the resin composition or laminate film according to thepresent invention is suitably usable for a wide range purposes includingindustrial packaging such as: those in the fields of medical,electronics, chemical and mechanical; more specifically, packaging offeed for pets, agricultural chemicals and fertilizer, and package fortransfusion; and semiconductor packaging, packaging of an oxidativeagent (or an agent susceptible to oxidation), precision materialpackaging, etc.

Further, the laminate, laminate film or shaped article according to thepresent invention is suitably usable as a shaped article in the form ofbottle, tray, etc., to be used for a squeezing-type bottle of mayonnaisejuice, soy sauce, edible oil, sauce, food tray for microwave oven, cupsfor yogurt, etc.

The resin composition according to the present invention may exhibit agood gas barrier property in any form or shape of those as describedhereinabove, while retaining a good folding resistance and a good filmstrength.

What is claimed is:
 1. A laminate structure comprising a first materiallayer having a first and second surface, a barrier layer of a resincomposition disposed on the first surface of the first layer, and asecond material layer disposed on at least one of the second surface ofthe first layer or the barrier layer; in which said resin compositioncomprises: (a) a polyvinyl alcohol resin having a saponification degreeof not less than 70% and (b) an inorganic laminar compound having anaspect ratio of 200 to 3000 having a layered crystal structure, whereinunit crystal layers are mutually stacked to form said layered structure,and said inorganic laminar compound is swollen or cleft when in asolvent; said composition has a volume ratio of: inorganic laminarcompound/polyvinyl alcohol, in the range of 5/95 to 30/70, and saidlaminate structure exhibits an oxygen permeability of not more than 0.5cc/m²-day-atm under the condition of 30° C. and 60% relative humidity.2. The laminate structure according to claim 1, which has the shape of afilm.
 3. The laminate structure according to claim 1, wherein either thefirst material layer or the second material layer comprisespolypropylene and is dry laminated to the barrier layer.
 4. The laminatestructure according to claim 1, wherein the barrier layer is formed byapplying a coating liquid containing the resin composition mixture ontoa surface of the first material layer or second material layer and thendrying the resultant coating.
 5. The laminate structure according toclaim 1, wherein the barrier layer is formed and laminated onto at leastone of the first and second material layers.
 6. The laminate structureaccording to claim 1, wherein the first material layer or the secondmaterial layer is extrusion-laminated onto the barrier layer.